Benchmarking of DFT functionals for the kinetics and mechanisms of atmospheric addition reactions of OH radicals with phenyl and substituted phenyl‐based organic pollutants

Abstract • OH addition reactions play a pivotal role in the atmospheric transformation of a number of phenyl and substituted phenyl‐based persistent and toxic organic pollutants. Here, we screened appropriate DFT functionals to predict reaction mechanisms and rate constants ( k OH ) of the • OH additions by taking benzene and substituted benzenes (C 6 H 5 F, C 6 H 5 Cl, C 6 H 5 Br, C 6 H 5 CH 3 , C 6 H 5 OH) as model compounds. By comparing the k OH values calculated with DFT methods to experimental values, we found that the ωB97 functional is the best among the 18 functionals considered (using the basis sets 6‐31 + G(d,p) for optimizations and 6‐311++G(3df,2pd) for single point energy calculations) in the temperature range of 230‐330 K. In addition, we found that some other functionals performed well in specific conditions, e.g., BMKD3 is good for benzene, halogenated benzenes and C 6 H 5 CH 3 , and CAM‐B3LYP is good for the reaction of C 6 H 5 OH at room temperature. Based on the diversity of the electronic structures of the selected model compounds and the frequent occurrence of certain substituents (CH 3 , OH, F, Cl, and Br) in the target compounds, the functionals recommended here can be used for future study of the reaction mechanisms and k OH values for • OH addition to phenyl and substituted phenyl‐based persistent and toxic organic pollutants.